Vibration eliminating means



April 1932- T. M. EDISON 1,855,570

. VIBRATION ELIMINATING' MEANS Filed Feb. 28, 1928 "WI z, W I

d v 4; B 29 v 1Q A FWMLQ W SMM M x da aaw A TORNEY Patented Apr. 26,1932 UNITED STATES'PATENT OFFICE THEODORE M. EDISON, OF EAST ORANGE,

NEW JERSEY, nssrenon TO THOMAS A.

EDISON, INCORPORATED, OF WEST ORANGE, NEW JERSEY, A CORPORATION OF 'NEWJERSEY VIBRATION ELIMINATING MEANS Application filed February 28, 1928.Serial No. 257,776.

My, invention relates to vibration eliminating means and moreparticularly to such means as applied to or embodied in mechanisms whichare subj ectable to forces tending to set up vibrations therein.

The principal object of my invention is t eliminate, or at least greatlyreduce, vibrations and especially those of certain definite frequencies,from mechanisms which are su'bjectable to forces tending to set up suchvibrations. \Vhile my invention is applicable to the elimination orreduction of all kinds of periodic vibrations whether of torsion ortranslation, the most satisfactory results are obtained by the use of myinvention in cases where the vibrations to be eliminated or reduced havethe character of simple harmonic motions.

The basis of my invention may be briefly described as follows:

A system may be made up of elastic means coaeting with a mass or massesso as to have a natural period of vibration dependent upon the constantsof the system. If such a system is applied to a mechanism subjected tothe action of a periodic force and if the natural period of vibration ofthe system is made equal to the period of the impressed force and if thesystem is so arranged as to be capable of displacements which will setup a resultant force in the line of and equal and opposite to theimpressed force, I find that the system will then actually tend tovibrate in such a way that the force it sets up in the mechanism willexactly neutralize the impressed force. Thepresence of friction andvarious damping effects would prevent the neutralization from beingperfect, but if these factors are kept small and the amplitudes of thevibrations in the system are not so great as to cause substantialdeviations from Hookes law, the system will neutralize most of theeffect upon the mechanism, of the impressed force of the givenfrequency.

As a rule a system such as just described,

, \vhe.n applied to a mechanism,while effective in such a way that thefrequency which it tends to intensify will not coincide with thefrequency of any force which may be impressed upon the mechanism. Ingeneral this intensifying frequency will depend not only upon theconstants of the system,

but also upon the constants of the mechanism to which it is to beapplied. For this reason, it will be necessary to modify the constantsof the system, which may be properly described a vibration eliminator,to suit the conditions under which it operates.

It is to be understood that my invention is not only applicable topractically all types of mechanisms for eliminating or reducing allkinds of periodic vibrations as indicated above, but is also capable ofbeing expressed in many different mechanical forms. For the purposes ofillustration, however, I shall proceed to describe a simple embodimentof my invention as applied to a mechanism having an unbalanced rotatingelement, as, for example an' electric motor having an unbalancedarmature shaft.

In the drawings accompanying and forming a part of this specification:

Figure l is a front elevation of'an electric motor having appliedthereto vibration eliminating means in accordance with my invention;

F1 2 is an end elevation lookm from the 0. right in 1* 1g. 1;

F 1 s. 3 and 4 are dia rammatic views res b spectively 'o-rresponding toFigs. 1 and 2, and

illustrating how the vibration eliminating motor, and 3 a pulley orflywheel secured to the shaft. The armature shaft 2 of this motor isunbalanced, this unbalanced condition being indicated by the thickenedpart 4 of the flange of the pulley or flywheel 3, and when the motor isoperated at its normal con- 5 stant speed, there will be impressedthereon,

' because of such unbalanced condition, a periodic force tending to setup in the motor vibrations having the character of simple harmonicmotions. In this particular case, the system or vibration eliminatingmeans applied to the mechanism comprises the four vibrators Aa, Bb, C0and Dd arranged as indicated about the armature shaft 2. Each of thesevibrators consists of a weighted resilient rod having such dimensionsthat the natural period thereof is substantially the same as the periodof rotation of the shaft 2 when the motor is operating at normal speed,in other words, each vibrator is tuned to the frequency of the periodicforce impressed on the motor by reason of the unbalanced conditionofshaft 2, that is, to the frequency of the vibrations which it isdesigned or intended to eliminate or reduce. The rods, (1, b, c and d ofthe vibrators are preferably suitably fixed at one end to the motorframe 1, and have the weights A, B, C and D respectively securedthereto, as by set-screws 5, at points remote from their said ends. Forbest results, the axes of the four vibrators should be in a common planewith the axis of rotation of the unbalanced rotatable element or shaft2, and they are shown as so located.

While the vibrations which the impressed periodic force tends to set upin the motor illustrated herein can be very greatly reduced by the useof any number of said vibrators less than four, in this case it isessential in order to most effectively neutralize the effect of saidimpressed force, to employ four such vibrators arranged as shown, ratherthan one, two or three. The reason for this willbe apparent from aconsideration of Figs. 3 and 4 and the explanation which follows. Inthese two diagrammatic figures the motor frame, armature shaft andvibrators of the structureshown in Figs. 1 and 2, are respectivelyrepresented by corresponding arts designated 1, 2, 'A'a',.Bb, C'c' and'61,

shaft 2 is represented by the mas M eccen- 'trically mounted on therotatable element or shaft 2. It will apparent that when the motor isoperating the force impressed thereon by reason of the unbalancedcondition of its shaft, as represented by the mass M (Figs. 3 and 4)always acts in a radial direction with reference to the axis of rotationof said shaft,

and that the line of action of this force while continually changing asthe shaft rotates, always remains in a slngle plane which is normal tosaid axis of rotation. The amount and line of action of this impressedforce, for the position of the mass M shown in Fig. 3, is

represented in this figure by the arrow F, the

and the unbalanced condition of the armature amounts and lines of actionof such force for the full and dotted line positions M and M ofthe-mass, as shown in Fig. 4, are respectively represented in the latterfi re by the full and dotted arrows F and F and the locus of the amountsand lines of action of such force are represented by a circular planefigure indicated by the dotted circle G in Fig. 4. It will be seen thatthe system or vibration eliminating means as shown comprises two pairsof vibrators Aa, B?) and C0, Dd (Figs. 1 and 2), or A'a', Bb' and C'c',D'd (Figs. 3 and 4), respectively applied to the motor at either side ofthe plane of action of the impressed force, and that the vibrators Aa,C0, or Aa, C'c', and B6, Dd, or Bb', Dci', of said pairs of vibratorsare respectively applied to the motor at either side of the axis ofrotation of the motor shaft.

- Referring now to Fig. 3, as the mass M, in the normal rotation ofshaft 2', reaches the position shown, the force F which it exerts on theshaft is theoretically exactly neutralized bythe forces, represented bythe arrows F, F F and F, respectively exerted by the vibrators A'a',B'b, C(: and D'd'. In case that the algebraic sum of the five forces'shown, as well as the algebraic sum of the couples produced by theseforces, will be zero. (This peculiarity may be utilized in dynamicbalancing machlnes). If the vibrators C'c and Dd were omitted thecombined forces exerted by vibrators A'a and Bb' would be equal andopposite to the force exerted by the mass M, but the resultant line ofaction of said combined forces would not then coincide with or passalong the line of action of said force exerted by mass. M and this wouldleave an unbalanced couple. In Fig. 4, the full line position of mass Mcorresponds to the position of said mass shown in Fig. 3, and the fullline arrows F 5 represents the amount and line of action of the-forcethen exerted on shaft 2' by this mass and corresponds to the arrow F inFig. 3. The combined resultants of the forces exerted by the pairs ofvibrators A a, C'c and Bb', D'd', which resultants are respectivelyrepresented by the solid arrows F andF, will then be equal and oppositeto the force F. The direction of each of the said resultants of theforces exerted by the pairs of vibrators Aa, 0'0 and Bb', Dd'continually changes as shaft 2 rotates, but is always radial with.reference to the axes of the respective pair of vibrators and in a planenormal-thereto, the loci of such resultants respectively being twocircular plane line circles K and L. When the mass reaches the dottedline position M (Fig. 4) the force then exerted thereby, the amount andline of action of which is represented by the dotted hne arrow F 1Sneutralized by the combined resultants of the forces then exerted by thepairs of vibrators Aa, Cc and Bb, Dd', the amounts and directions ofwhich resultants are respectively properly represented by the dottedline arrows F and F. It will now also be-apparent that in case thevibrators disposed at either side of the axis of rotation of shaft 2'were omitted, while the combined forces exerted by the remainingvibrators would be equal and opposite to the force due to the mass M,the resultant of such combined forces would not be in the line of actionof the said forceexerted by mass M and an unbalanced couple wouldresult.

In case it is desired to eliminate vibrations from a mechanism due to aperiodic force impressed on the mechanism and acting in a fixed line,this can be accomplished by employing a system or vibration eliminatorcomprising but a single vibrator so applied to the mechanism as to exerta force which will act in the same line as the action of the impressedforce. Such an arrangement is shown in Fig. 5 wherein 1? represents amechanism and F theamount and line of action of a periodic forceimpressed on such mechanism and acting in a fixed line.. To

,v eliminate the vibrations which the force F tends to set up in themechanism 1 I employ a system comprising the single mass E resilientlyconnected to and supported from said mechanism by a coil spring S, theends of which spring are respectively fixedly secured to the mechanismand the mass. T his system is preferably so designed that its naturalperiod of vibration is substantially the same as the period of theimpressed force F and is connected to the mechanism 1 so that the forceF it exerts will act in the same line as the impressed force F.

- In the torsional case where the object is to eliminate oscillatoryvibrations from a rotary element, the simplest form of system orvibration eliminator to use for attaining such object would probably bea flywheel elastically connected to the rotary element in such a manneras to make the natural period of oscillation thereof equal to the periodof the oscillations which it is designed to eliminate.

As hereinbefore indicated my vibration eliminating means is especiallyadapted for application to mechanisms which are subjected to impressedforces of constant magnitude and frequency. In mechanisms where theseconditions are not present the eliminating means will be less effective,due to transient effects.

Having now fully .described my invention, what I claim as new and desireto protect by Letters Patent is as follows:

1. The combination with a mechanism subjecta-ble to the action of animpressed force tending to set up Vibrations of a substantially definiteperiod, of means for reducing such vibrations comprising a plurality ofvibrators each consisting of a mass elastically connected to saidmechanism, said means having a natural period of vibration substantiallythe same as the period of the vibrations which it is designed to reduce,the said vibrators being so applied to said mechanism that the resultantline'of action thereof substantially coincides with the line of actionof the impressed force, substantially as described.

2. The combination with a mechanism subjectable to the action of animpressed force tending to set up vibrations of a substantially definiteperiod and substantially of the character of simple harmonic motions, ofmeans for reducing such vibrations comprising a plurality of vibrationseach consisting of a mass elastically connected to said mechanism saidmeans having a natural period of vibration substantially the same as theperiod of the vibrations which it is designed to reduce, the saidvibrators being so applied to said mechanism that the resultant line ofaction thereof substantially coincides with the line of action of theimpressed force, substantially as described.

3. The combination with a mechanism comprising an unbalanced rotatableelement which when rotated at a given speed tends to set up vibrationsof a substantially definite period in said mechanism, of means forreducing such vibrations comprising two vibrators respectively appliedto said mechanism at either side of the axis of rotation of saidelement, each of said vibrators consisting of a weighted resilientmember fixedat one end to said mechanism, said vibrators having anatural period of vibration substantially the same as the period of thevibrations which' it is designed to reduce, substantially force actingin a plane and tending to set up vibrations of a substantially definiteperiod in said mecahnism, of means for reducing such vibrationscomprising two vibrators respectively applied to said mechanism oneither side of the said plane of action of said force, said vibratorshaving a natural period of vibration substantially the same as theperiod of the vibrations which it is designed to reduce, substantiallyas described.

5. The combination with a mechanism comprising a frame and an unbalancedrotatable element mounted on said frame and which when rotated at agiven speed exerts, by reason of its unbalanced condition, a forceacting in a plane and tending to set up vibrations of a substantiallydefinite period in I said mechanism, of means for reducing suchvibrations comprising two pairs of vibrators each consisting of aweighted resilient member fixed at one end to said frame, said pairs ofvibrators being respectively applied to said mechanism at either side ofthe said plane of action of said force, the vibrators of each of saidpairs of vibrators being respectively applied to said mechanism ateither side of the axis of rotation of said element, and all of saidvibrators having a natural period of vibration substantially the same asthe period of the vibrations which it is designed to reduce,substantially as described.

6. The combination with a mechanism comprising a frame and an unbalancedrotatable member mounted on said frame and which when rotated at a givenspeed exerts, by reason of its unbalanced condition, a force acting in aplane and tending to set up vibrations of a substantially definiteperiod in said mechanism, of means for reducing such vibrationscomprising two pairs of vibrators each consisting of a weightedresilient rod fixed at one end to said frame, said pairs of vibratorsbeing respectively applied to said mechanism at either side of the saidplane of action of said force, the vibrators of each of said pairs ofvibrators being respectively applied to said mechanism at either side ofthe axis of rotation of said member, all of said vibrators having anatural period of vibration substantially the same as the period of thevibrations which it is designed to reduce, and the axes of all of saidresilient weighted rods being in a common plane with said axis ofrotation, substantially as described.

7. The combination with a mechanism comprising an unbalanced rotatablemeans which when rotated at a given speed tends to set up vibrations ofa substantially definite period in the mechanism, of means for reducingsuch vibrations comprising a vibratory system having a plurality ofmasses each elastically connected to such mechanism, the natural periodof vibration of said system being substantially the same as the periodof the said vibrations which it is designed to reduce, such system beingso applied to said mechanism that the effective line of action thereofat any instant substantially coincides with the line of action of theforce to which said mechanism is subjected by reason of the unbalancedcondition of the said rotatable February, 1928. O0

means, substantially as described.

This specification signed this 27th day of THEODORE M. EDISON.

